Generally, in many occasions, an injectable liquid should be continuously injected to a patient. At this time, a liquid injection apparatus is used, and the liquid injection apparatus includes a filter device for removing impurities and air contained in the injectable liquid.
FIG. 12 is a perspective view showing an example of a conventional liquid injection apparatus, which may be referred to in U.S. Pat. No. 4,781,698.
A liquid injection apparatus 1000 includes an injectable liquid storing means 102 such as a bottle or pack where an injectable liquid is stored, and a flexible extension tube 104 extending from the injectable liquid storing means 102 to transport the injectable liquid supplied from the injectable liquid storing means 102. A dropping unit 106 partially inserted into the injectable liquid storing means 102 to drop the injectable liquid is integrally provided at an upstream end of the extension tube 104, and a control means 108 for controlling the amount of the supplied injectable liquid by blocking the flow of the injectable liquid flowing along the extension tube 104 is provided in the middle portion of the extension tube 104. In addition, there is provided a filter device 100 for filtering the supplied injectable liquid to remove impurities and air in the supplied injectable liquid, and a distal end connector 110 to which an injection needle N inserted into the body of a patient is detachably coupled is provided at the rear end of the corresponding extension tube 104.
Here, the extension tube 104 is provided to have the same inner diameter over the entire moving path of the injectable liquid, and instead of the injection needle N, a catheter well known in the art may also be coupled to the distal end connector 110 of the extension tube 104. A cap (not shown) is coupled to the distal end connector 110 so as to prevent the injectable liquid from being contaminated before the liquid injection apparatus 1000 is used. To use the liquid injection apparatus 1000, the corresponding cap is removed and wasted from the distal end connector, and the injection needle N or catheter is coupled thereto.
In addition, if a user (a nurse or the like) inserts the injection needle N into the body of a patient and then completely controls the amount of injected liquid by using the control means 108, the injectable liquid stored in the injectable liquid storing means 102 is discharged and supplied by small quantity, flows along the extension tube 104, and then, is injected into the body of the patient through the injection needle N coupled to the distal end connector 110.
Meanwhile, if impurities (for example, glass fragments generated in opening a glass ampoule) or air is injected together with an injectable liquid into the body of a patient, such impurities or air may damage the blood vessel or brain of the patient and cause a fatal danger. Therefore, in order to prevent this problem, the filter device 100 described above is provided on the path of the extension tube 104, and the capillary tube is provided in a distal end of the extension tube 104 connected to the filter device 100. The capillary tube installed in the distal end of the extension tube 104 prevents the medicine causing a fatal damage to the organ of the patent when injected fast, such as an anticancer medicine or antibiotics, from being excessively injected.
An example of the filter device 100 of the above liquid injection apparatus 1000 is shown in FIG. 13. Referring to the sectional view of FIG. 13, the filter device 100 includes filter receiving plates 100a-1 and 100a-2 made of synthetic resin provided at an outer side thereof to be spaced apart from each other in parallel to define a predetermined space therein, and both ends of the filter receiving plates 100a-1 and 100a-2 are converged and connected to the extension tube 104 so that the internal space communicates with the extension tube.
Two thin sheet-type filters 100b-1 and 100b-2 in parallel with each other are housed in the internal space defined by both the filter receiving plates 100a-1 and 100a-2. The liquid permeable filter 100b-1 is provided at the side where an injectable liquid flows in, and the gas permeable filter 100b-2 is provided at the next, wherein the filters 100b-1 and 100b-2 are made of porous synthetic resin material with a predetermined mesh. In addition, in the filter receiving plate 100a-2 in which the gas permeable filter 100b-2 is provided, an air discharge hole 100a-2-1 is formed at a corresponding location.
Therefore, in the conventional filter device 100 as shown in FIG. 13, if the injectable liquid supplied from the injectable liquid storing means 102 flows into the filter device 100, impurities such as glass fragments contained in the corresponding injectable liquid are filtered off while the injectable liquid passes through the liquid permeable filter 100b-1, and then, if the corresponding injectable liquid passes through the gas permeable filter 100b-2, the air is discharged to the outside through the air discharge hole 100a-2-1 after the injectable liquid passes through the gas permeable filter 100b-2. However, the conventional filter device has a problem in that a flow rate of the injectable liquid is lowered since two filters 100b-1 and 100b-2 blocks the flow path of the injectable liquid. In addition, the conventional filter device has a structural limit in that the air in the injectable liquid is not entirely discharged through the air discharge hole 100a-2-1 after passing through the gas permeable filter 100b-2, but partially flows into the extension tube 104. Moreover, the capillary tube installed in the distal end of the extension tube 104 should be sealably connected to the filter device 100, and at this time impurities of adhesive components flow into the filter device and/or the capillary tube.
In order to overcome the above problems, the present inventors have suggested new filter devices and a liquid injection apparatus having the same. These new devices are configured to effectively remove air or solid impurities such as glass fragments in the medicine. Examples of such new devices are disclosed in Korean Patent Application Nos. 10-2006-0033027 and 10-2007-0051334. These filter devices are excellent, but they can be improved further in common with other excellent technologies.
Particularly, in the technical field of the present invention, there are unceasing demands on the improvement of a filter device capable of effectively removing air and solid impurities such as glass fragments in a medicine and allowing sealable connection with a capillary in the extension tube without adhesive while minimizing a change in flow rate of the medicine.